Hi Calmy,
Come to think of it, if you are confident with your skills and experience, and if others doesn't appreciate your hard work, effort and your contribution, I believe somewhere else, someone will sees the effort in you. I'm sure they are other workplaces, with better environment, and culture will appreciate your value and your contribution.
Also, have you thought of why did your company GM refuse to get you in full time? Some of the factors you might want to sit down and think about it, here are some possible factor:
1) Company budget are limited - If they bringing in one full time, perhaps more expense to the company weighing all the benefits as a full time stuff.
2) They do not see your significant contribution in the company? Did you show or let them realize your contribution and the effort you put in for the company?
3) Instead of feeling negative emotion, you can focus on what needs to be done next. You don't really have to feel what others feel about you. You are you, you are unique in your own way. & this is your life, you decide to move on, or decide to make a change and decide to be better tomorrow.
What do you think?